In “painted tongue” plants, wild type flowers are red, but many other flower col
ID: 192135 • Letter: I
Question
In “painted tongue” plants, wild type flowers are red, but many other flower color variants have been isolated and some of them breed true, including blue and lavender. A geneticist finds that alleles of a single gene determine whether flowers are red, blue or lavender.
Results of some of her crosses are shown here:
True-breeding parents F1 progeny F2 progeny (self-pollinating F1s)
red x blue All red 102 red, 33 blue
Red x lavender All bronze 84 bronze, 43 red, 41 lavender
a. Indicate the relationship between the alleles that display red x blue traits, and the relationship between the alleles that display red and lavender traits.
b. If the bronze F1 progeny of the red x lavender cross are crossed with true-breeding red plants, what progeny classes do you expect to find in what proportions?
Explanation / Answer
True-breeding parents F1 progeny F2 progeny (self-pollinating F1s)
red x blue All red 102 red, 33 blue
Red x lavender All bronze 84 bronze, 43 red, 41 lavender
b. Ans-
Since red and lavender alleles are co-dominant, so we could write them as R red and R lav .
Let F1 progeny are R red R lav and true-breeding red R red R red
R red R lav × R red R red
½ R red R lav ½ R red R red
So, the expected progeny will be half bronze and half red